To provide a method and an apparatus for feeding dampening water in an offset printing machine wherein quality of printing is good, it is unnecessary to add various additives such as an alcohol and an etching liquid, running cost can be decreased, and a level of contamination of a waste liquid is low and is environment-friendly.

The dampening water is made into an active monomolecular water, and after it is adjusted by controlling it into a specified concentration of the active monomolecular water, it is fed into a dampening water apparatus of the printing machine. The apparatus for feeding the dampening water is constituted of a device for generating the active monomolecular water, a means for detecting the concentration of the active monomolecular water of the dampening water, and a device for controlling the dampening water which controls to feed the generated active monomolecular water and controls operations of the apparatus for feeding the dampening water and the device for generating the active monomolecular water.